So much about Zetsuai 1989 is sad, but oh god the music; the lyrics. It's all so dark and angsty and sad and lovely and crazy. And the three singers who've sung for it have all been absolutely amazing in different ways; I will be forever grateful that all three were able to really channel the crazy depths of emotion in Koji's voice/character.
I haven't really thought about Z89 in a while, but there was a time that I couldn't stop listening to all of the music (re-reading the manga and re-watching the anime go without saying). Saishuushou by Takehide Inoue, while not sung by my favorite iteration of Koji (Hayami Sho, he of the Divinely Deep, Spontaneous-Orgasm-Inducing Voice), is probably the saddest and most beautiful of all the songs and was one that I played on repeat non-stop for a very, very, very long time.
I don't think you have to even really understand what the lyrics mean to hear the sadness in the song (much like
Ue wo muite arukou (aka "Sukiyaki Song") by Sakamoto Kyu), but if you want to know what's being said, here is a page with the
original Japanese (both kanji and romaji) and the English translation of lyrics. ETA: Favorite line: inochi nado nakushitemo / anata dake ireba ii [should i lose my life and still more / if only you remain, it's enough]
Click to view
List of all days.